In healthy bone, formation and degradation are in balance. This is disturbed in Paget’s disease. Many patients are symptom-free, while others experience various symptoms. Paget’s disease is named after its first describer, the British physician Sir James Paget. It is also called “Paget’s disease of the bone” (to distinguish it from Paget’s carcinoma, “Paget’s disease of the breast”).
Osteodystrophia deformans
The technical term osteodystrophia deformans provides an appropriate description of the condition: osteodystrophy refers to abnormal bone remodeling that results in decreased bone quality; deformans stands for “disfiguring” as a possible consequence of the disorder.
How does this disease develop and who is affected?
The cause is still not clear. However, there is evidence that it may be a disorder caused by viruses (especially measles viruses) that does not become apparent until years to decades after infection (slow virus infection). Since there is a familial and geographical clustering of the disease, there is probably also a hereditary predisposition.
The bone-eating cells (osteoclasts) needed to remodel the bone are more active than in healthy individuals, resulting in increased degradation of bone tissue. The body tries to compensate for this accelerated degradation by a hasty build-up (by means of osteoblasts), which, however, leads to the newly formed bone being of inferior quality.
The consequences of this increased degradation and build-up are bone thickening and irregularities, bending and reduced load-bearing capacity of the skeleton. Mostly men over 40-50 years of age are affected, the incidence of the disease is 50 to 300 cases per 100,000 inhabitants. Thus, although Paget’s disease is rare, it is still the second most common bone disease after osteoporosis.
How does the disease manifest?
In many affected individuals, there are no or hardly any symptoms, so it is not uncommon for the diagnosis to be made by chance during an X-ray performed for another reason. If symptoms do occur, they primarily affect areas where the bones are under heavy stress: Lumbar spine, pelvis and legs, possibly also skull, clavicles and upper arms.
- The increasing deformations may be visible from the outside (for example, saber-shaped bending of the shin, curved posture, facial changes (the hat suddenly becomes too small).
- There may be – usually diffuse, pulling – pain at the sites of remodeling (especially at night) – back pain is particularly common. Due to the changes, the adjacent joints are subjected to increased stress, which increasingly leads to discomfort there as well.
- Spontaneous bone fractures, severe headaches, hearing loss and dizziness attacks (due to deformation of the bone in the inner ear) and nerve paralysis (for example, because deformed vertebrae press on the nerve canal) are other possible consequences.
- Increased bone loss leads to increased calcium excretion, which can lead to kidney stones.
- Rare late complication (about 1% of cases) is a malignant bone tumor (osteosarcoma).
